NIOSH investigators are investigation whether tungsten oxide fibers are more persistent in the lung than non-fibrous tungsten-containing particles. Result of these solubility and biopersistence experiments will provide data to support scientific-based decision making regarding the solubility of specific suboxides of tungsten oxide fibers relative to tungsten-containing particles. Dissolution experiments in artificial airway epithelial lining fluid were completed. All the samples from these studies have been sent to the analytical lab for quantification of dissolved tungsten. Dissolution experiments in artificial macrophage phagolysosomal fluid began in late in FY09.